Home | History | Annotate | Download | only in utils 
      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef _LIBS_UTILS_CONDITION_H
     18 #define _LIBS_UTILS_CONDITION_H
     19 
     20 #include <stdint.h>
     21 #include <sys/types.h>
     22 #include <time.h>
     23 
     24 #if defined(HAVE_PTHREADS)
     25 # include <pthread.h>
     26 #endif
     27 
     28 #include <utils/Errors.h>
     29 #include <utils/Mutex.h>
     30 #include <utils/Timers.h>
     31 
     32 // ---------------------------------------------------------------------------
     33 namespace android {
     34 // ---------------------------------------------------------------------------
     35 
     36 /*
     37  * Condition variable class.  The implementation is system-dependent.
     38  *
     39  * Condition variables are paired up with mutexes.  Lock the mutex,
     40  * call wait(), then either re-wait() if things aren't quite what you want,
     41  * or unlock the mutex and continue.  All threads calling wait() must
     42  * use the same mutex for a given Condition.
     43  */
     44 class Condition {
     45 public:
     46     enum {
     47         PRIVATE = 0,
     48         SHARED = 1
     49     };
     50 
     51     Condition();
     52     Condition(int type);
     53     ~Condition();
     54     // Wait on the condition variable.  Lock the mutex before calling.
     55     status_t wait(Mutex& mutex);
     56     // same with relative timeout
     57     status_t waitRelative(Mutex& mutex, nsecs_t reltime);
     58     // Signal the condition variable, allowing one thread to continue.
     59     void signal();
     60     // Signal the condition variable, allowing all threads to continue.
     61     void broadcast();
     62 
     63 private:
     64 #if defined(HAVE_PTHREADS)
     65     pthread_cond_t mCond;
     66 #else
     67     void*   mState;
     68 #endif
     69 };
     70 
     71 // ---------------------------------------------------------------------------
     72 
     73 #if defined(HAVE_PTHREADS)
     74 
     75 inline Condition::Condition() {
     76     pthread_cond_init(&mCond, NULL);
     77 }
     78 inline Condition::Condition(int type) {
     79     if (type == SHARED) {
     80         pthread_condattr_t attr;
     81         pthread_condattr_init(&attr);
     82         pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
     83         pthread_cond_init(&mCond, &attr);
     84         pthread_condattr_destroy(&attr);
     85     } else {
     86         pthread_cond_init(&mCond, NULL);
     87     }
     88 }
     89 inline Condition::~Condition() {
     90     pthread_cond_destroy(&mCond);
     91 }
     92 inline status_t Condition::wait(Mutex& mutex) {
     93     return -pthread_cond_wait(&mCond, &mutex.mMutex);
     94 }
     95 inline status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime) {
     96 #if defined(HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE)
     97     struct timespec ts;
     98     ts.tv_sec  = reltime/1000000000;
     99     ts.tv_nsec = reltime%1000000000;
    100     return -pthread_cond_timedwait_relative_np(&mCond, &mutex.mMutex, &ts);
    101 #else // HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE
    102     struct timespec ts;
    103 #if defined(HAVE_POSIX_CLOCKS)
    104     clock_gettime(CLOCK_REALTIME, &ts);
    105 #else // HAVE_POSIX_CLOCKS
    106     // we don't support the clocks here.
    107     struct timeval t;
    108     gettimeofday(&t, NULL);
    109     ts.tv_sec = t.tv_sec;
    110     ts.tv_nsec= t.tv_usec*1000;
    111 #endif // HAVE_POSIX_CLOCKS
    112     ts.tv_sec += reltime/1000000000;
    113     ts.tv_nsec+= reltime%1000000000;
    114     if (ts.tv_nsec >= 1000000000) {
    115         ts.tv_nsec -= 1000000000;
    116         ts.tv_sec  += 1;
    117     }
    118     return -pthread_cond_timedwait(&mCond, &mutex.mMutex, &ts);
    119 #endif // HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE
    120 }
    121 inline void Condition::signal() {
    122     pthread_cond_signal(&mCond);
    123 }
    124 inline void Condition::broadcast() {
    125     pthread_cond_broadcast(&mCond);
    126 }
    127 
    128 #endif // HAVE_PTHREADS
    129 
    130 // ---------------------------------------------------------------------------
    131 }; // namespace android
    132 // ---------------------------------------------------------------------------
    133 
    134 #endif // _LIBS_UTILS_CONDITON_H
    135